Microbial approaches to optically active sulfur-containing fluorinated compounds

A γ-Fluoro β-Acetoxypropyl Sulfonium Salt as an Equivalent of a (Fluoromethyl)vinyl Sulfonium Salt: Reagent for the Facile Synthesis of Monofluoromethylated Cyclopropanes or Aziridines

“…Although both the precursor compounds 7 and 8 are known, we were unfortunately unable to prepare compound 8 according to the reported procedure, forcing us to find a new method for its preparation. 5 Consequently, we examined the regioselective ring-opening reaction of the known epoxy sulfide 9 6 with potassium hydrogen difluoride (KHF 2 ) as a fluorine source under various conditions as shown in Table 1. 7 Under the optimized reaction conditions (Table 1, entry 5), the epoxy sulfide 9 smoothly underwent ring opening with four equivalents of KHF 2 in the presence of tetrabutylammonium dihydrogen trifluoride (TBADT, 10 mol%) and TBAF (1 mol/L in THF; 1.5 equiv) at 95 °C for 16 hours to give regioisomer 8 exclusively in 90% yield (GC/MS).…”

Yeast‐Mediated Stereoselective Synthesis

“…Similarly, 1,1-bis(p-tolylthio)ketones [148,149] as well as β-keto dithioesters have been reduced by baker's yeast; the yields were low, but high ee values (>95%) could be achieved. The reduction of β-keto sulfides gave the corresponding alcohols with ee values ranging between 70 and 94% [150,151]. In general, the reduction of these compounds with yeast seems difficult and proceeds best only at low concentrations of the substrate [150].…”

Regio- and stereoselective synthesis of vicinal fluorohydrins

“…The corresponding sulfoxide was less selectively reduced by baker's yeast (53% ee) (Scheme 11) [49]. The enantioselectivity was improved when the p-tolyl thioether (97% ee), [50] the sulfoxide (85% ee) [51] or the corresponding sulfone (87% ee) [50] were subjected to microbial reductions using baker's yeast.…”

“…However, the first attempts with sulfur substituted 2-acetoxy-1-fluoropropanes with lipase MY were not very selective (Scheme 62) [49].…”

“…The reaction was much less selective, when a phenylthio substituent was placed in the molecule [49]. Acetic acid esters of chlorofluoromethyl alcohols on the other hand showed better selectivity with the same lipase (Scheme 64) [155].…”